Controllable drive unit with combustion engine and generator

ABSTRACT

A system of an internal combustion engine (VM) with rpm actuator (DRS), a refrigerator (AM) and a direct drive mechanically coupling the engine to the refrigerator, and a control unit including a thermostat for maintaining the internal temperature of the refrigerator at a predetermined set point value (SW), is improved by (a) a refrigerator thermostat setting, (b) a refrigerator external temperature sensor coupled, and (c) an engine speed tachometer (DM), all coupled to the control unit; (d) the control unit determining an optimal engine rpm from the inputs and characteristic function stored in a memory device (ST) of the control unit; and (e) the rpm actuator adjusting the rpm to the optimal rpm value.

FIELD OF THE INVENTION

The invention relates to a drive unit for an operating device consistingof an internal combustion engine and a machine driven by it and anelectrical consumer, wherein the output to be provided fluctuates withdemand. Possible machines for this are, for example, pumps, compressors,generators, drive units etc. in the most varied operating devices.

DESCRIPTION OF THE RELATED ART

Such drive units are controlled in such a way that the internalcombustion engine is respectively switched off when the actual value ofa quantity to be controlled exceeds a predetermined set value in eitherdirection, and it is started up again when the actual value of thecontrolled quantity exceeds the set value by a predetermined differencein either direction, i.e. with a hysteresis, after which the internalcombustion engine and the drive unit are then operated at full load rpm.

Such a two-point control operation has many disadvantages. The engine isoften operated at low temperatures in the start-up phase, which resultsin a loss of efficiency and an increase in pollutants in the exhaust gasas well as increased wear. Further than that, loud noise is generatedsince operation is at full load rpm.

A drive unit for a heat pump with an internal combustion engine whichdrives a compressor and a generator is known from EP-A 0 152 121,wherein a measurement of the output requirements and a corresponding rpmregulation of the internal combustion engine is provided there.

SUMMARY OF THE INVENTION

Based on this state of the art, it is the object of the invention tocreate a drive unit with a further optimized degree of efficiency whichallows a silent, environmentally friendly, economical andmaterial-saving operation.

This object is attained in that the difference between the actual valueof the controlled quantity and the actual value, as well as theparameters affecting the controlled quantity, are measured, wherein therespective output requirements are determined from output requirementcoefficients assigned to these measured values. In accordance with this,a characteristic output curve for the engine rpm is then determined fromcharacteristic values stored in a control device and is supplied to theinternal combustion engine for regulating its rpm.

An electrical generator, which directly and/or via at least one voltageand frequency converting unit supplies electrical consumers, isadditionally coupled with the internal combustion engine. Synchronousand asynchronous three-phase current generators are used in thisconnection. The electrical output is measured and is reported via anappropriate signal to the control unit and is added to the outputrequirements there. It is furthermore provided that in the rare caseswhere there is no demand for output or where it is so small that theinternal combustion engine provides an unnecessary amount of output evenat idle speed, a controlled disconnection of the engine takes place. Inthe process the electrical installation continues to be operated by theinternal combustion engine. As soon as there is a demand for outputagain, the connection is restored and work is resumed.

The demand determination is converted into engine rpm in that, forexample, data from a table of a characteristic output curve in relationto the rpm are stored in the control device, wherein the respectiveoptimum rpm are determined by means of a poll and possibly additionallyby means of an interpolation from the table values of the characteristicline.

The set rpm are provided to an rpm control device of the internalcombustion engine in the form of a set signal. An rpm signal derivedfrom the engine is supplied to the control device in the form of anactual signal. The difference with the rpm set value is then provided bythe control device to an rpm actuator of the internal combustion engine.In a Diesel engine this rpm actuator can be a servo motor for a strokeadjustment of a fuel injection device, for example.

The output requirement coefficients of the parameters which have aneffect on the control quantity are determined on the basis ofexperimental values or are exactly calculated at the time of placing theentire device into operation, if this is possible. These coefficientsare advantageously optimized by means of a learning program.

In accordance with the invention, the internal combustion engine isoperated at very low rpm near its lower permissible rpm limit. Becauseof this it maintains its operating temperature, generates little noiseand has a high degree of efficiency. In its size and its outputdimensions the internal combustion engine can be designed to meet anaverage value which lies considerably below the peak load, if the latteronly occurs seldom, since in this way engines can tolerate peak loadsincreased in this way for short periods of time.

The operational values, such as pollutant emission and fuel consumption,are also suitably optimized to fit an average operation. This results inconsiderable advantages and fuel savings in contrast to the design formaximum operation.

The use of this controllable drive unit is particularly advantageous inconnection with cooling installations for a chamber to be cooled, inparticular the interior of a refrigerated transport vehicle, bus or thelike having an internal combustion engine and a compressor driven by itwith a coolant circuit connected to it, which comprises a condenser, anexpansion valve and at least one evaporator, whose return line is runback to the aspiration side of the compressor, wherein the coolingoutput in relation to a predetermined set temperature isthermostatically controlled by means of an interior thermometer.

Such cooling installations are generally known. They are controlled sothat the compressor is respectively switched off when the interiortemperature of the refrigerated chamber falls below a predetermined settemperature and it is turned on again when the interior temperatureexceeds the set temperature by a predetermined difference, i.e. with ahysteresis, whereupon the engine and the compressor are again operatedat full load rpm. This two-point control operation of the coolinginstallation has many disadvantages. The engine is often operated at lowtemperatures in the start-up phase, which results in a loss ofefficiency and an increase in pollutants in the exhaust gas as well asincreased wear. Furthermore, loud noise is generated since operation isat full load rpm. Also, at high cooling output and when only a smalloutput in the medium is required, condensation occurs at the evaporator,which leads to an undesired increase in moisture in the cooled air,which can cause corrosion and which, particularly in buses, is unhealthyfor the passengers.

The respective cooling output requirements are determined respectivelyfrom a difference between the measured interior temperature and the settemperature as well as from a difference between the exteriortemperature, which is continuously measured by means of at least oneoutside thermometer, and the set temperature, and from the coolingrequirement coefficients of the installation to be cooled assigned tothese coefficients, and in accordance with this a set engine rpm isdetermined from characteristic values of a cooling output engine rpmcharacteristic curve stored in a control device and is provided to theinternal combustion engine for controlling its rpm.

The cooling circuit only requires a small reservoir for the coolingmedium. The size and output dimensions of the Diesel engine can bedesigned to meet an average value which lies considerably, for exampleby 30 to 40%, below the peak load, which only occurs for a few hours peryear under extreme weather conditions, since engines can tolerate suchincreased peak loads for only a short time. The operational values, suchas pollutant emission and fuel consumption, are also suitably optimizedto fit an average operation. This results in considerable advantages andfuel savings in contrast to the design for maximum operation.

It is further advantageously provided that in the rare cases where thereis no demand for cooling output or where it is so small that theinternal combustion engine provides an unnecessary amount of output evenat idle speed, turn-off or disconnection of the engine takes place.Since only a small condenser reservoir has been provided, the respectivesubsequent restarting or re-connection of the engine will take placepractically without counterpressure from the compressor, because thecondensate then is already completely evaporated and pressureequalization prevails in the cooling circuit.

The cooling output requirement is continuously determined from thedifference between the exterior skin temperature of the cooling chamberand is determined in a supplementary manner by a difference between theinterior temperature and the set temperature, which is necessary whenmaterials to be cooled have been recently placed inside or particularlyin case of heat sources in the cooling chamber, for example in case ofpeople.

Furthermore the energy output of a possibly present electrical on-boardcircuit is continuously monitored and included in the cooling outputrequirements.

Beside a measurement of the exterior temperature of the surface of thecooling chamber, it is suitably provided to perform a radiationmeasurement of incoming infrared radiation, in particular sunlight, onthe various surfaces of the refrigerated vehicle, particularly thewindow areas, so that the radiation portion can be directly included inthe calculation of cooling output requirements.

The inclusive cooling output requirement report makes it possible toprovide as exactly as possible an adaptation of the compressor rpm tothe respective requirements, so that practically no stoppage of thedriving engine need take place. The requirements determination isconverted into engine rpm or compressor rpm in that, for example, datafrom tables of a characteristic cooling output curve in relation to therpm is stored in the control device and the respectively optimum rpm aredetermined by means of an interrogation and possibly additionally by aninterpolation from the table values of the characteristic curve.

The set rpm are provided to an rpm regulating device of the internalcombustion engine as the set signal. The rpm regulator can also be anintegrated part of the control device. The latter is provided with anrpm signal derived from the engine or the compressor as the actualvalue. The difference with the rpm set value is then provided by thecontrol device to an rpm actuator of the Diesel engine. This rpmactuator is for example a servo motor for a stroke adjustment of a fuelinjection device.

In case the exterior temperature is considerably lower than thepredetermined interior temperature there is the possibility that coolingis no longer required, so that it is then provided that the engine withthe compressor is completely stopped or is uncoupled. In this connectionthere is a continuous comparison of the interior temperature with alower temperature threshold value and when this falls below it, theengine is switched off or disconnected. As soon as the lower temperaturethreshold is again exceeded by a predetermined amount, the drivingengine is started or connected and the compressor is thereby put backinto operation.

In accordance with the invention, an electrical three-phase currentgenerator is connected with the driving engine and operates the blowersin the evaporator and condenser, which is of great importance,particularly when the vehicle is operated in idle. Since the engine onlyturns slowly during low cooling output, the generator also delivers athree-phase current of lower frequency, so that the blowers also turnslowly in adaptation to the low cooling requirements and use littleenergy and make little noise.

In addition, the generator can supply in an advantageous manner anon-board circuit of the bus or vehicle via a voltage and frequencyconversion device, so that the main engine can be turned off even duringprolonged stops and the airconditioning engine with the generatorsupplies the lighting system, the sound system, etc. via the converter.

In a further embodiment the generator is fixedly coupled with thedriving engine and the compressor is connected with it via acontrollable clutch. In this way it is possible to disengage the clutchwhen the lower temperature threshold value is downwardly exceeded, whilethe electrical system continues to be operated by the driving engine. Assoon as a renewed cooling demand is generated, the clutch is reconnectedand cooling operations begun.

For calculating the cooling output from the temperature differencesbetween the set temperature and the measured interior temperature andthe measured exterior temperature, as well as from a radiationmeasurement and an electrical output consumption, associated outputcoefficients are determined, which have been obtained from the surfacevalues, the insulation and radiation resorption coefficients as well asthe experimental values of the heat transfer from the exterior air tothe surface during stops and operation while moving. When the entiredevice is started, the coefficients are determined on the basis ofexperimental values. These coefficients are advantageously optimized bymeans of a learning program which, respectively as a function of theappearance of the requirements for stopping the cooling unit and as afunction of exceeding the set temperature by a predetermined valuewithin observations periods, which are greater than the thermal timeconstants of the heat transfer through the insulation layer, makescorrections which incrementally counter the amount of upward or downwardexcess, and thereby optimizes successively.

All of the above measures result in an optimally comfortable climaticadjustment, particularly in airconditioning units of passenger vehicles,in which the interior temperature only shows very slight fluctuationssince practically no compressor shut-off takes place and the operationof the evaporator is performed by means of a moderate evaporationoutput, so that there is practically no icing and there is only alimited increase in the humidity of the exhaust air from the evaporator.

Most electrical consumers, such as electric motors, are designed in sucha way that they can operate within a defined frequency bandwidth andvoltage bandwidth. This frequency range lies, for example in Europe,between 45 Hz and 55 Hz. With an appropriate design of the electricmotors, the range can be correspondingly greater, for example it cancover a range between 40 Hz and 60 Hz. With an incandescent lamp thecurrent frequency within this frequency range is of no consequence atall. This permissible frequency bandwidth therefore represents a controlrange for adaptation to load changes, wherein converters (rectifiers)are not needed.

The generator frequency is controlled by the control device within thepermissible frequency bandwidth, and thus also the output voltage andthe current via the engine rpm of the internal combustion engine, insuch a way that the electrical output of the generator corresponds tothe actual load requirements.

Employment of the controllable drive unit in accordance with theinvention is of interest in all cases where machines are used whichrequire current and are employed in changing locations with and withoutconnections to the power lines. If there is no connection to the powerlines, current is supplied by means of the generator by therpm-controlled internal combustion engine.

The controllable drive unit can also be employed in an advantageousmanner in connection with a wind power installation.

BRIEF DESCRIPTION OF THE DRAWING

Exemplary embodiments are represented in the drawings and will bedescribed in detail below. Shown are in:

FIG. 1, a block circuit diagram of a first embodiment,

FIG. 2, a block circuit diagram of a second embodiment,

FIG. 3, a block circuit diagram of a third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an internal combustion engine (VM), which usually is aDiesel engine, to which a machine (AM) is flanged and drives anoperating device (AV). A control device (ST) is provided for thecontinuous output calculation, which is connected on the input side withan actual value sensor (M1) for a controlled quantity as well as withone or several value sensors (M2) for parameters (PW) affecting thecontrolled quantity. It is furthermore advantageously provided to inputa set value (SW) for the controlled quantity into the control device(ST) by means of an input keyboard (ET). The control device (ST)contains a suitably programmed microprocessor containing outputrequirement coefficients and a table correlating the rpm of the machine(AM) with the operating output in its memory. Output requirementcoefficients are assigned to the measured actual value (IW) of thecontrolled quantity and the measured parameter values (PW) as a functionof the predetermined set value (SW). From these coefficients the controldevice (ST) determines the set rpm of the internal combustion engine(VM).

The engine rpm are picked up at the engine shaft by a tachometer (DM)and a corresponding actual rpm signal (SI) is supplied to the controldevice (ST). From the difference with the engine rpm, the control devicedetermines an output signal (SD), which directly actuates an rpmactuator (DRS) of the internal combustion engine (VM). If the control ofa Diesel engine is involved, the rpm actuator (DRS) preferably sets thestroke of the injection device by means of a servo motor.

An electrical generator (G), preferably a three-phase current generator,is disposed on the engine shaft. It supplies an electric consumer (V2)and a battery (AKKU) directly and/or indirectly via a converter (UF1),which delivers a standardized d.c. voltage. The charge current for thebattery (AKKU) flows via a charge control circuit (LK) and is disruptedby it when the battery (AKKU) is completely charged. The converter (UF1)and/or the battery (AKKU) supply a further converter (UF2), whichoutputs a predetermined voltage of a predetermined frequency (forexample 200 V, 380 V and 50 Hz, 60 Hz) to one or several consumers (V1).A current measuring device (IM1) is located downstream of the generator(G), whose measuring signal is proportional to the electrical outputtaken and is supplied to the control device (ST) as a further inputsignal for output calculation. In addition to this, a further currentmeasuring device (IM2) is provided, which determines the electricaloutput taken from the battery (AKKU) and the converter (UF1) and whosemeasuring signal is also provided to the control device (ST).

A clutch (K) is disposed between the machine (AM) and the internalcombustion engine (VM), which can be operated by the control device(ST). In this way the machine (AM) can be disconnected when there is nodemand for mechanical work output. However, the generator (G) continuesto be driven by the internal combustion engine (VM). To compensate theoutput peaks at the generator (G) occurring when the machine (AM) isconnected and disconnected, the former is preferably equipped with aflywheel.

The battery (AKKU) is used as a buffer during load fluctuations, untilthe internal combustion engine (VM) is readjusted. It can be relativelysmall for this. But it can also be used for bridging during frequentlong periods of low load, wherein the internal combustion engine (VM) isturned off and is automatically electrically started via the starter(START) by the battery (AKKU) before its charge is depleted.

Besides the actual value (SW), it is also possible to enter calculatingcoefficients as well as a lower and an upper threshold value for thecontrolled quantity into the control device (ST) by means of the inputkeyboard (ET). Furthermore, an output device (A), for example an LCDdisplay, is provided for displaying the respectively predetermined setvalue (SW) as well as the respective actual value (IW).

Preferably the converters (UF1, UF2) are equipped in a known manner withsemiconductor switches, capacitors and throttles, so that they containno mechanically wearing parts.

A controllable drive unit, in particular for cooling devices, isschematically represented in FIGS. 2 and 3.

FIG. 2 shows an embodiment without a generator, which is not a part ofthe invention.

FIG. 2 shows an internal combustion engine (VM), which normally is aDiesel engine, on which a compressor (2) is flanged, which supplies acoolant circuit. The coolant is supplied in the compressed state to acondenser (7), from which the condensate runs into a condensatereservoir (6), from which it enters the evaporator (4) through anexpansion valve (5), from where the expanded coolant gas flows backthrough the aspirating side into the condenser. The evaporator islocated in a cooling chamber (R) which is enclosed on all sides byinsulation (I). In case the cooling chamber (R) is the interior of abus, it consists partially of glass surfaces, of course, a part of whichare pervious to heat radiation, so that the radiation heat must also beremoved by means of the cooling device. Associated blowers (40, 70) areprovided for the effective removal of cold or heat from the evaporator(4) or the condenser (7) and are electrically driven. Compared withconventional cooling installations, the reservoir (6) is designed tohave a very low capacity, because the cooling device operatescontinuously and therefore practically no storage of coolant is needed.

A control device (ST) is provided for continuous cooling outputcalculation, whose input side is connected with an interior thermometer(TI), Several exterior thermometers (TA) disposed on the exterior skinof the cooling chamber (R), one or several heat radiation measuringdevices (SM), which are assigned to the window surfaces in particular. Asuitably programmed microprocessor is disposed in the control device(ST) and contains in a memory the output coefficients as well as a tablerepresenting the correlation of the compressor rpm with the coolingoutput. On the output side the control device (ST) supplies a signalrepresenting the set rpm (SD) to an rpm regulator (DR) which, on theother side, is supplied with an actual rpm signal (SI) which had beentaken off the compressor or engine shaft by means of a tachometer (DM).The difference signal from the rpm regulator acts on the supply of theinternal combustion engine.

FIG. 3 shows a further embodiment of the device, wherein an electricalgenerator (G), which preferably is a three-phase current generator, isdisposed on the engine shaft. It supplies the three-phase currentblowers (40, 70), so that their rpm are proportional to the engine rpmand therefore proportional to the cooling output requirements. Inaddition, the generator (G) supplies a converter (80), which outputs astandardized voltage of a standardized frequency which supplies anon-board circuit (V) having consumers, such as lights, audio system andsignal devices. The on-board circuit (V) is passed over a currentmeasuring device (IM), whose measuring signal is proportional to theelectrical output taken up and is supplied to the control device (ST) asa further input signal for calculating the cooling output.

In the example provided, the function of the rpm regulator is integratedin the control device (ST), for which reason the rpm measuring signal ofthe tachometer (DM) is supplied to the control device (ST) as a furtherinput signal. The output signal of the control device (ST) directlyactuates an rpm actuator (DRS) which, if this relates to the control ofa Diesel engine, preferably sets the stroke of the injection device bymeans of a servo motor. A keyboard (ET), which is served by means of aninput program of the microprocessor, is connected at the input side ofthe control device for entering the various cooling requirementcalculation coefficients, including the surface values, the specificinsulation values, the window areas, the specific radiation absorption,etc., as well as the compressor characteristic in relation to its rpm.

The respectively desired set temperature as well as the lowertemperature threshold value are furthermore entered by means of theinput keyboard (ET). An output device (A), for example a digitaldisplay, is used for the control of the entered data and for the displayof the respectively predetermined set temperature as well as therespective interior temperature.

As illustrated, it is provided in a special embodiment that a clutch (K)is disposed between the compressor (2) and the engine (VM), which can beactuated by means of an actuating signal from the control device (ST).In this way the electrical generator (G) can be operated by the engine(VM), even if there is no requirement for cooling output, or if only thecooling output from the coolant contained in the reservoir (6) isconverted, wherein the blower (40) conveys the cooled air from theevaporator (4) into the cooling chamber (R).

Preferably the converter (80) is equipped in a known manner withsemiconductor switches, capacitors and throttles, so that it contains nomechanically wearing parts.

Most electrical consumers, such as electric motors (blowers,compressors), are designed in such a way that they can operate within adefined frequency bandwidth around a rated frequency (f_(N)) between alower frequency value (f_(u)) and an upper frequency value (f_(o)). Thisfrequency range lies, for example in Europe, between 45 Hz and 55 Hz.With an appropriate design of the electric motors, the range can becorrespondingly greater (for example between 40 Hz and 60 Hz). With anincandescent lamp the current frequency within this range is of noconsequence at all. This permissible frequency bandwidth thereforerepresents a control range for adaptation to load changes, wherein aconverter (rectifier) is superfluous.

With a synchronous generator, the output voltage (U_(a)) is proportionalto the rpm with which the generator (G) is driven. With a load change,the output voltage (U_(a)) of the generator (G) is adapted to the actualload by the rpm change of the internal combustion engine (VM) whichdrives the generator (G). Within the permissible frequency bandwidth,the frequency change occurring as a result of this does not hamper thefunction of the electrical consumers. The output voltage (U_(a)) of thegenerator is measured and supplied to the control device (ST). From thestored generator rating data and the generator frequency (f), thecontrol device (ST) determines a generator set voltage (U_(s)).

The deviation of the generator output voltage (U_(a)) from the generatorset voltage (U_(s)) occurring because of the inner resistance (R_(G)) ofthe generator when a current (I) flows in the case of a load is used fordetermining the current value and is correspondingly taken intoconsideration during adjustment. The connection is described by thefollowing equation:

    U.sub.a =U.sub.s -I·R.sub.G.

The generator (G) is adjusted by means of the frequency (f) in such away that it is operated close to the lower frequency (f_(u)) at lowloads and, with increasing output requirements, increasing current (I)the set frequency (f_(s)) is increased. This is expressed by means ofthe following equation:

    f.sub.s =f.sub.u +(f.sub.o -f.sub.u)·I/I.sub.Max.

In this case, I_(Max) is the current supplied by the generator if it isoperated at the upper frequency (f_(o)).

In the following claims, "refrigerator" means a cooling installation fora chamber to be cooled, and "generator" means an electrical DC generatoror AC alternator.

What is claimed is:
 1. In a controllable drive unit operating device includingan internal combustion engine (VM) able to rotate at an rpm and including an rpm actuator (DR, DRS) for controlling the rpm of the engine, a refrigerator (AM) and a direct drive mechanically coupling the engine to the refrigerator, a control unit includingthermostat means for maintaining an internal temperature of the refrigerator at a predetermined set point value (SW), the improvement comprising:(a) refrigerator internal temperature setting input means coupled to the control unit; (b) a sensor of a refrigerator external temperature, the sensor being coupled to the control unit; (c) a tachometer (DM) disposed on the engine for measuring an engine speed, the tachometer being coupled to the control unit; (d) the control unit including means for acceptingthe refrigerator internal temperature setting, the external temperature, and the engine speed measured by the tachometer, and for determining therefrom an optimal value of the engine rpm according to values of an output characteristic function stored in a memory device (ST) of the control unit; and (e) means for causing the rpm actuator to adjust the rpm toward the optimal value determined by the control unit.
 2. The improvement according to claim 1, wherein the control unit includes self-learning means to adjust the characteristic function.
 3. The improvement according to claim 1, wherein the refrigerator includes an evaporator blower motor (40) and a condenser blower motor 70), and the improvement comprises:an electrical generator (G) directly coupled mechanically to the engine and directly coupled electrically to the evaporator blower motor (40) and the condenser blower motor (70), whereby the evaporator blower motor (40) and a condenser blower motor (70) turn at rotational speeds corresponding to the engine rpm.
 4. The improvement according to claim 3, wherein the generator is a three-phase generator and the evaporator blower motor (40) and the condenser blower motor (70) are three-phase blower motors.
 5. The improvement according to claim 4, wherein the generator (G) supplies a converter (UF1), which supplies a predetermined three-phase voltage to at least one electrical load.
 6. The improvement according to claim 5, wherein the characteristic function includes the electrical load and the internal temperature of the refrigerator as independent variables.
 7. The improvement according to claim 4, comprising means for comparing a respectively measured actual value (IW) of the internal temperature with a predetermined threshold value which lies above or below the respectively predetermined set point value by a predetermined difference and then, when the actual value (IW) falls above or below the threshold value, disconnecting the internal combustion engine (VM) in a controlled manner from the refrigerator (AM) via a clutch (K), while the three-phase current generator (G) continues to be driven and, when thereafter the actual value has again attained the predetermined set point value, again connecting the internal combustion engine (VM) in a controlled manner with the refrigerator (AM).
 8. The improvement according to claim 5, wherein the electrical load includes a battery (AKKU) and the improvement comprises means for charging the battery, and whereinthe charge current (IL) for the battery (AKKU) is switched off by a charge control circuit (LK) as soon as the battery (AKKU) is fully charged.
 9. The improvement according to claim 5, wherein the electrical output taken from the three-phase current generator (G) is determined by means of a current measuring device (IM1) and/or the electrical output taken from the battery (AKKU) and the converter (UF1) is determined by a current measuring device (IM2) and is added to the output requirements in the memory device (ST).
 10. The improvement according to claim 1, wherein when there is no requirement for mechanical work output or only a low requirement for electrical output, the internal combustion engine (VM) is switched off in a controlled manner, wherein the battery (AKKU) is then used for bridging the current supply and electrically starts the internal combustion engine (VM) by means of a starter (START) before its charge is depleted.
 11. The improvement according to claim 5, wherein the three-phase current generator (G) includes a flywheel with an appropriate mass for compensating output peaks during disconnection from and connection to the refrigerator (AM) of the internal combustion engine (VM).
 12. The improvement according to claim 5, wherein a generator frequency (f) is controlled via the engine rpm by the memory device (ST) within a permissible frequency bandwidth between a lower frequency value (fu) and an upper frequency value (f_(o)) around a rated generator frequency (f_(N)) in such a way that a generator output voltage is matched to a respective electrical output consumption.
 13. The improvement according to claim 1, wherein the refrigerator includes a cooling chamber (R) having a cooling device therefor, a compressor (2) driven by the engine, and a coolant circuit connected to the cooling device including a condenser (7), an expansion valve (5) and at least one evaporator (4), a return line of which is brought back to an aspirating side of the compressor (2), and an interior thermometer (TI) and an exterior thermometer (TA), and, means for determining a respective cooling output requirement from a difference between the measured interior temperature and the set point value as well as from a difference between the exterior temperature, which is continuously measured with the exterior thermometer (TA), and the set point value, and from cooling output requirement coefficients assigned to differences thereof and, in accordance therewith, determining the optimal value of the engine rpm from characteristic values of the characteristic function for cooling output engine rpm stored in the memory device (ST) and is supplied to the rpm actuator (DR) of the internal combustion engine (VM).
 14. The improvement according to claim 13, wherein a plurality of the exterior thermometer are disposed on surfaces of various outside areas of the cooling chamber.
 15. The improvement according to claim 13, comprising at least one exterior heat radiation measuring device (SM) disposed on the cooling chamber, a respective radiation measuring signal of which is linked with a radiation penetration coefficient of window surfaces and means for adding the measuring signal to the cooling output requirements.
 16. The improvement according to claim 13, wherein the memory device (ST) includes the rpm actuator (DR) and the rpm actuator is supplied with an rpm signal from the tachometer (DM) disposed on the internal combustion engine (VM), a difference in respect to a respective motor set rpm is supplied to the rpm actuator (DRS) of the engine (1).
 17. The improvement according to claim 1, wherein the rpm actuator (DRS) comprises a stroke adjustment device of a fuel injection device.
 18. The improvement according to one of claim 13, wherein in the memory device (ST) the respectively measured interior temperature is compared with a predetermined lower temperature threshold value lying a predetermined temperature difference below the set point value and, when the interior temperature falls below the lower temperature threshold value, the internal combustion engine (VM) is switched off or disconnected from the compressor (2) in a controlled manner and when thereafter the interior temperature has again reached the set point value, the internal combustion engine (VM) is started again or connected to the compressor (2) in a controlled manner.
 19. The improvement according to claim 13, wherein the generator (G) supplies a converter circuit (80) which delivers a predetermined voltage and frequency to an on-board circuit (V) of a bus or vehicle.
 20. The improvement according to claim 13, including means for determining respectively the electrical output taken up by the on-board circuit (V) by a current measuring device (IM) reporting to the memory device (ST) and adding to the respective cooling output requirements in the memory device (ST).
 21. The improvement according to claim 13, including means for storing cooling output requirement coefficients in the memory device (ST) and respectively at a time of a stoppage of the compressor (2) and respectively at a time the set point value is exceeded by a predetermined amount, such that an incremental increase or decrease of a corresponding cooling output requirement coefficient in an opposite direction takes place via an optimization program. 